[USB2_Soft / UART Loopback] Error in Communication Device Class (Abstract Control Model) / Zero length descriptor references

[Semnodime]

usb2_soft

usb_uart_loopback.gprj

dmesg ->

[  +0,000000] usb 1-4: new high-speed USB device number 1 using xhci_hcd
[  +0,156252] usb 1-4: New USB device found, idVendor=33aa, idProduct=0000, bcdDevice= 1.00
[  +0,000007] usb 1-4: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[  +0,000002] usb 1-4: Product: USB2Serial
[  +0,000001] usb 1-4: Manufacturer: Gowinsemi
[  +0,000619] cdc_acm 1-4:1.0: Zero length descriptor references
[  +0,000004] cdc_acm: probe of 1-4:1.0 failed with error -22

[kyonmiriam]

Hi, I have understood your problem. Sorry we haven't had time to test on Linux yet because we lack such a device. But I guess this issue may be caused by a small bug in the USB descriptor. We can see such a line of error prompts in USBTreeView.

This corresponds to line 212 in the src/usb_descriptor.v file in the project. You can see that h02 is written here.

Maybe changing this to h00 and rebuilding the project will help.